1. Field of the Invention
The present invention relates to a lens device and focus control method capable of omitting a component for sliding operation and also improving operability of absolute position indicating operation and relative position indicating operation in focus adjustment.
2. Description of the Related Art
Conventionally, as depicted in FIG. 8, a lens device has been known in a lens barrel 91 has an outer circumferential part provided with a focus ring 93 capable of sliding operation forward and backward (an arrow direction in the drawing) in an optical axis O direction.
Also, Japanese Patent Application Laid-Open No. 2007-178633 (hereinafter referred to as Patent Literature 1) discloses a lens device in which a focus ring of a relative position indication type and a focus ring of an absolute position indication type are placed on an outer circumferential part of a lens barrel 1 and switching is mechanically made to enable either one of these two focus rings by performing a sliding operation of the focus ring of the relative position indication type along an optical axis direction.
A lens device has also been known in which a touch sensor is provided on an outer circumferential part of a lens barrel and an indicating operation is possible with the touch sensor (refer to Japanese Patent Application Laid-Open No. 2009-169266, Japanese Patent Application Laid-Open No. 2010-117444, Japanese Patent Application Laid-Open No. 10-111448: hereinafter referred to as Patent Literatures 2 to 4 respectively).
A structure is also known in which a key is operated for rough adjustment for focusing is performed and a wheel is operated for fine adjustment (refer to Japanese Patent Application Laid-Open No. 2009-31654: hereinafter referred to as Patent Literature 5).
In the structure as depicted in FIG. 8 where switching is made between absolute position indication and relative position indication by a mechanical sliding operation of the focus ring, there are problems as follows: reflecting the force amount and feel at the time of switching is not easy, the number of components for sliding operation increases on the outer circumference of the barrel, and detection of switching is difficult.
While Patent Literatures 2 to 4 disclose the structure in which a focus indicating operation can be performed with a touch sensor, these patent literatures do not describe at all switching between absolute position indication and relative position indication. Patent Literature 5 does not have any disclosure regarding touch operation.
It can be thought that a touch sensor for absolute position indication and a touch sensor for relative position indication are provided on the outer circumferential part of the lens barrel. If such a structure as described above is assumed, it is hard for an operator with an operation feeling of rotating a focus ring with reference to a regulation end (a rotation end) that regulates a rotation range to use the touch sensor to operate with reference to the regulation end, and therefore a new problem occurs in which the structure would not be acceptable to the operator.
Moreover, Patent Literature 2 describes that a touching finger is moved quickly for rough focus adjustment and the touching finger is moved slowly for fine focus adjustment. However, in general, there is a difference in slowness and quickness of finger movement between the feeling of the operator and detection on a lens device side. Therefore, there is another problem in which, in practice, it is difficult to perform operation so as to distinguish between rough adjustment and fine adjustment only with slowness and quickness of finger movement.
In particular, for television camera operators operating by hand with feeling while viewing a finder, the sense of touch is important, and further improvement in operability is demanded.